Intro to cabbage maggots

cabbage fly

The post I was hoping not to write…

Last year in early April, I planted a dozen brassica starts (kale & cauliflower). They grew happily at first, but about a month later, I noticed they were wilting suddenly. A brief research suggested a possible cabbage maggot infestation. I dug one plant up, and sure enough, a few fat white maggots were drilling through the base of the stem, just below the soil surface. All the plants were dug up then, the nasty larvae picked-off, and starts were re-planted, fingers crossed. In the end, most of the kale made it, and most of the cauliflower did not – they have a weak root system, and are more sensitive to root damage.

The cabbage root fly (delia radicum) looks like a small house fly. In early spring, it lays eggs at the base of brassica family plants (kale, cabbage, brussels sprouts, cauliflower etc.). When the larvae hatches, they drill through the stem down, feeding on the delicate green flesh, disrupting the plant’s nutrients flow and also the structure. The flies like cool weather, so later planted crops (such as now) are usually fine, while the early crops can be completely destroyed by this pest.

There are few ways to prevent the flies from laying their eggs, one of which iscollar the floating cover (reemay), which I consider a bit of a unsightly pain in the neck. Instead, I tried protective “collars” – pieces of cardboard which look like this:

Today, I came to the garden after extended weekend camping trip to San Juan Islands (don’t get me started on the incredible wildlife experience which peaked at the J-pod orca parade – flops and breaches and all…). Here, on my plot, one of my cauliflowers withered, and I knew my effort was not completely successful. Yup, I pulled the plant up, the poor main root, completely chewed-off, and five brownish pupae were scattered in the soil (see the two eggish things in the picture). Squish! The larvae feeds about three weeks, and since the rest of the plants appear to be healthy, I think we are out of the danger zone. One plant out of six is not a bad score, and the rest of the plants have more room to spread out – cauliflower can get quite huge, you know… So watch out for them root maggots!

photo 1(2)photo 2(2)


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